Circuit interrupter



June 2, 1942- o. s. JENNINGS Erm. 2,284,825

cmcumlmx-:RRUPTER Fiied sept. 8, 1958 l t fatcnted June-2, 1942 2.284.825 cracnrr m'raalturrsa cum s. 1mm, mutui-gn, ma um s.

Gann

arg, Pa., asaignors to Westing- & Manufacturing Company.

East Pittsburgh, Pa.. a corporation of Pennsyl- Vania Anuman september- 8, 193s, semi No. 22am 12 calms.' (ci. zoo- 11m The invention relates to electrical switchesvor circuit interrupters, in general, and more particularly to circuit interrupters of the type having an electro-responsive or 'thermal trip eiement for automatically causing operation of the t'ixiiterrupter in response to predetermined condions.

Circuit interrupters having thermally responsive trip elements for tripping the interrupter in response tooverloads of predetermined magnitude and duration may be materially aifected by changes in ambient temperature. If the ambient temperature is higher than that for which the interrupter is calibrated, a part of the release .movement of the thermal trip element occurs even before the overload arises, with the result that the interrupter is tripped open either at a lower current value or at a given current value in a shorter time. Conversely, if the amibent temperature is lower than that for whichI the interrupter has been calibrated, the required overload release travel of the thermal trip element is increased so that the interrupter will be tripped either at a higher current value or at a given current value only after a longer lapse of time. In some applications it is particularly important that the trip characteristic of the circuit interrupter remain-unaffected by ambient temperature changes.

An object of the invention is the provision of a circuit interrupter, the trip characteristic of which remains substantially unaffected by c in ambient temperature.

Another object of the invention is the provision of an electrical switch which will be automatically operated in response to deiinlte predetermined overload conditions irrespective of any variations in ambient temperature.

Another object of the invention is the provision of a circuit interrupter embodying a thermal trip element and a means for compensating for changes in ambient temperature, the compensating means being so arranged that it is substantially unaffected by heat generated at the thermal trip element or within the circuit interrupter.

. The novel features that are considered characteristic of the invention are set forth in partlcular in the appended claims. The invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of one embodiment thereof when read in conjunction with the accompanying drawing, in which: v

Figure l is a vertical sectional vlew or a circuit breaker constructed in accordance with theinvention;

Fig. 2 is an enlarged fragmentary sectional view showing the details of the thermal trip'devicev `and the means for compensating for changes in ambient temperature, the parts being shown in their normal positions;

Fig. 3 is a view similar to Fig. 2, showing the thermal trip element and the ambient temperature compensating means iiexed in responseto a rise in ambient temperature; and

Fig. 4 is a plan view of the trip device shown in F18. 3.

Referring to the drawing, the circuit breaker comprises; in general, a base 1, a cover 9, contact means indicated generally at Il, an operating mechanism indicated generally at I3, and a trip device indicated generally at I5. r

The base 1 is constructed of molded insulating material and forms a support for the various elements of the circuit breaker. The cover 9 which is also of molded insulating material, is secured to the base i by suitable means such as bolts (not shown), which pass through aligned openings formed in the base and cover. A pair of end terminals i9 are mounted in suitable openings provided in the ends of the base 1 and these terminals form the means for connecting the breaker in an electrical circuit.

The contact means indicated generally at Il comprises a stationary contact 2| connected by a conductor strip 2l to one of the end terminals I9, a movable contact 25 carried by a resilient switch arm 21, and an arc-extinguishing means indicated generally at 29. The arc-extinguishing means is not an important part of the invention, and any suitable type may be used.

The movable contact 25 is secured to the free end of the resilient switch arm 21 by means of a rivet 30 and the opposite end of the switch arm 21 is secured to a channel-.shaped movable contact supporting frame 3l by means of a pair of rivets 32. The channel-shaped contact supporting frame Il is pivotally supported by means of a pivot pin 33 to the side walls of a metallic U-shaped main frame 35 secured to the base. y The operating mechanism vI3 of the circuit breaker comprises, in general, a bii'urcated operating member 31, a releasable member 39, a pair of toggle links 4| and 43, a pair of over-center springs 45 and an operating handle 41.

The operating member 31 has the lower ends of its legs pivotally supported on side walls of the main frame 35 by means of pivot studs 48. The upper end of the operating member 31 has secured thereto an arcuate closure member 49 of molded insulating material, which acts to close ber 99 is adapted to be normallyheldin latched tion, as will be described hereinafter. l n

The releasable member 39 is pivotally supported by means of a pivot pin 55 which extends between the side walls of the main frame 95..:

The releasable member hasa rearwardly .extentiel u ing portion 51 provided with a latch 50"which is .far described .is vtneriyjiis follows. with the parts in the position shownin Fig. l, that is. with the contact means in closed-circuit position 2,284, 825 leasable member 39following a tripping operathe circuit controlled by the breaker.

After a tripping operation, the breaker cannot be reclosed without nrst moving the operating circuit position with a snap action to interrupt handle 41 to the full open-circuit position. The vresetting movement of the operating handle v41 to the open-circuit position causes the resetting member 53 to engage and move the releasable member 39 in 'a counter-clockwise direction to the position shown in Fig. 1, in which' it is relatched by the trip device I 5.

I'he trip device comprises a thermally responsive trip element in the form of a -bimetaliic strip 63, which is pivotally mounted at its lower end on the base 1. The lower end of the bi- A metallic element is bent at a right angie and secured in .any suitable manner to a U-shaped bracket 65. The bracket 55 is plv tally mounted ons. U-shaped supporting bracket l1 by means ot a pivot pin 89 which extends through the side legs or the brackets Bland 51. The supporting bracket 51 is seated on the base 1 and yis rigidly secured thereto by a pair of downwardand the releasable member 39 held in its' normal y latched position by the trip device I5, let it be assumed that it isdesired to manually yopen.

the circuit controlledv by the'breaker. The operating handle 41 is moved from the closed p0- sition shown in Fig.Y 1 in a counter-clockwise direction to an open-circuit position at the oppo site end of the opening I. This movement of the operatingyhandle 41 to open position moves the operating member v31 in a counter-clockwise direction about its pivot axis 48. At a certain point in the opening movement oi the operends clinched over against a ating member 31, the over-centersprings i change their line of action with respect toh the pivot point 58 of the upper toggle link 4I and cause collapse of the toggle links 4I and 45. The

collapse of -the toggle links causes movement of the switch arm 21 in a counter-clockwise directionk to open-circuit position with a snap action.

4In manually closing the circuit breaker,` sub-l stantially the reverse action takes place. The y operating' handle is returned to the closed po-` sition shown in Fig. l. At a predetermined point in the closing movement ofV the operating'handle 41, the over-center springs 45 change their line of action with respect to the pivot point 59 and cause the toggle links 4I and 43 to assume their extended or in-toggle position as vshown in Fig. l. Movement of the toggle links to their extended position causes clockwise movement oi' the'movable contact supporting ,frame-vll and switch arm 21 Vto closed-circuit position with a snap action to eilect engagement of the movable contact 25 with the stationary contact 2|.

a clockwise direction about its pivot axis 55 by a component of force exerted by the-over-center ,springs 45, andthe trip device I5 under normal conditions holds the releasable member in its normal latched position against the biasing action of the springs 45. If ,an overload of predetermined magnitude and duration occurs in -ly extending projections 1I which openings' in the base 1 and have their vlower plate 15 engaging the underside of the base 1. Y

The upper end of the bimetal trip element V5I is provided with .an adjustable latchelement' in the form of an adjusting screw which is threaded-'through the free end oi the trip element 6I. The latch element 15 is normally adapted to overlapthe latch 55 carried by thereleasable member I9 to hold the releasable member in its normal positionshown in Fig. `1. The bimetallic trip element is connected in series circuit with the contacts 25.and 2| oi the circuit breaker by means of a'pair of ilexible series conductors 11 and 19, so as tolbe responsive-to the current iiowing in the controlled circuit. The

series conductor 11 has one end connected-to the` left-hand terminal I9 and its other end connected to the upper free end oi' the bimetallic trip element 63. The flexible series conductors 19 are secured to the bent toot of the bimetallic trip element B3 atene end and their Aother endsfar'e secured toa terminal strip Il.. 'I'he terminal strip 9| is secured to a horizontal extension ot the mounting bracket 51 by means of a screw $3 (Fig. 4). The' other end of the conducting strip II is connected by flexible series conductors 55 to the resilient switch arm 21.

The circuit through the breaker extends from the left-hand terminal I9 through the iiexible conductor 11,'bimetallic trip element filexible. I

- conductors` 19, conductor kstrip Il, iiexible `conthecircuit controlled by the breaker, the trip .device operates'to effect release'of the releasable member 39. The member 39 when released, is rotated in a clockwise direction about its pivot axis 55 by the springs 45 and 'at a predetermined point in its movement changes the line of action of the over-center springs 45 relative to the pivot pin 58 to-cause 'collapse otthe toggle links and resulting movement of the switch arm 21 to openof the circuit breaker inthe ductors 95, resilient switch ax'fm121 through the f y contacts 25 andli and the conducting strip 29 The releasable member 39 is always biased in Y s curs in the circuit controlled by the breaker, the

bimetallic trip element 53 is heated by the over-:- `load current and'ilexes `in afdirection away from the operating mechanism v.I9 to cause thelatch element 15 to release the releavsable member".

The release of the member Il etl'ects'opening manner previously described. i. After the circuit has been interrupted, the bimetallic trip returns to its normal topermit resetting f the circuit breaker.

pass through element 53 cools and Y position shown in Fig. 1,1

A perature of the trip element 63, and to insure that the breaker will be tripped open there is provided that the bimetallic strip 'andasse to-maintain the cali from the bimetallic sulating connection 93 is an important feature ilects in a direction away from the operating mechanism an amount proportional tothe rise in ambient temperature.

This decreases the amount of latch overlap between the latch ele-.

ment 'l5 and the latch 80, with the result that the breaker will be tripped open either at a lower current than that for which it was calibrated, or at a given overloadcurrent in a shorter period oi time. Conversely, if the ambient temperature decreases, the bimetallic trip element 63 will deect in a direction toward the mechanism i3 and tend to increase the amount of latch between the elements 1I and 60, with the result that the breaker will be tripped open. either at a higher current value than that for which it was calibrated, or at a given overload current after al longer period of time.

In order to prevent changes in ambient temirom affecting the trip characteristic in response to dennite predetermined overload conditions, irrespective of4 changes in ambient temperature, an ambient temperature compensating means comprising a bimetallic strip l1. The strip 81 is secured at one end by means of a rivet 89 in a recess provided on the underside of the base 1. The tree end of the bimetallic strip 81 is connected'to the bracket 65, which carries the t ip element 6I, through the agency of an adjusiing screw 9| and an insulator. The insulator 83 extends through a small opening in the base and is provided with a slot as adjacent' its upper end, which is engaged in a slot 91 formed in an extension 89 of 65. A' suitable spring, not shown. maybe provided ior biasing the bimetallic trip element in a clockwise direction about its pivot axis 69 to maintain the legs lillv oi the bracket B ln engagement with the lower edges of the slot 95 in the insulator 93.

The operation of compensating means ambient temperature the ambient temperature is briefly as follows. It the rises, the bimetallic trip element 63 is deflected toward the left away irom the operating mechanism I3. However, the bimetallic strip l1 is arranged so that it deiiects downwardly to cause the bracket and the bimetallic trip element clockwise,l direction to compensate for the ambient temperature deflection of the bimetallic trip element 63. This position of the parts is illustrated in Fig. 3. Conversely,l i! the ambient temperature decreases, the bimetallic trip element 83 deilects toward the operating mechanism i3.. At the same time, however, the bimetallic strip B1 is deilected upwardly by the decrease in ambient temperature to rotate the bimetallic trip element 63 in a counter-clockwise direction to compensate for. the ambient temperature deflection thereof. It will thus be seen l1 always maintains the same amount oi overlap between the latch the bracket 63 to partially rotate in a 'munter u element 1I and'the latch BI irrespective of.. any change in ambient temperature, so that the breaker will always be tripped open in response to definite predetermined overloads, irrespective of any changes in ambient temperature.

The mounting arrangement of the bimetallic strip I1 on the underside oijthe'base and away trip element il and theinof the invention since with this mounting arrangement and connection, the vbase I and the substantially completely heat insulaie the bimetallic strip l1 from the bimetallic trip element 03 and the other conducting parts of the circuit breake Thus heat generated at the bimetallic trip element l 0r internally With` in the circuit breaker is prevented from aiiecting the bimetallic strip l1. l

The adjusting screw 8i is accessible from outside of the circuit breaker casing and serves to adjust the trip characteristic of the bimetallic trip element 63. Turning the screw 9| in or out changes the amount of overlap betweenthe latch element 1l and the latch 80.

By varying the deilection characteristics oi. the bimetallic strips 63 and Il'l with respect to each other, the bimetallic trip element 63 may be under, fully, or over-compensated for changes in the ambient temperature. or arranged to give any other desired characteristic or compensation.

While the invention has been disclosed in accordance with the provisions ofA the patent statutes, it is to be understood that various changes in the structural details thereof may be macie without departing from the spirit of the invention. It is desired, therefore, that the appended claims be given the broadest reasonable interpltetation permissible in the light oi the vprior a We claim as our invention:

l. In a circuit nterrupter, relatively movable contacts for opening and closing the circuit. actuating means for opening and closing said contacts, means including a bodily movable ther mal control element heated in response to the current in the circuit and movable in response to predetermined overload conditions in the circuit to eilect actuation of said contacts, and a thermally responsive member-having one portion rigidly secured to a fixed support and -havture 2. In a circuit interrupten a pair of relative- .ly movable contacts for opening and closing the circuit, a bodily movable electro-responsive control element heated in response to the current in the circuit and movable a predetermined amount in response to predetermined current conditions to eiiect actuation of said contacts, and a bimetallicmember rigidly mounted at one end on ailxed support and having its free end connected to said control element by an adjustable heat insulating connecting means for bodily displacing said control element in response to changes in ambient temperature. v

3. In a circuit interrupter, relatively movable contacts for opening and closing the circuit actuating means for opening and closing said contacts, means including a pivotallymounted bimetallic trip element heated in response to the current in the circuit and movable in response to predetermined overload conditions to cause opening of said contacts, and a bimetallic mem- -ber having one end rigidly mounted on a ilxed support and its free en'd connected to said trip elementfor compensating for changes in ambient temperature.

4.1In a circuit interrupter, a casing, a vswitch member mounted in said casing `for movement -able when heated a predetermined amount by the passage of overload currents oi' predetermined magnitude and duration to cause movement of said switch member to open circuit po sition irrespective of the position ot said operating means, anda thermally responsive member mounted on the outside ,of said casing and connected Ito said thermal control element for lcompensating for changes in ambient temperature. f

5. In a circuit interrupter, a casing, relatively movable contacts mounted in said casing, a bimetallic trip Aelenient movably mounted in said casing and heated in response `to thel current flowing in' the circuit, said trip element being adapted to ex a predetermined amount in respense to predetermined overload conditions to cause opening of said contacts, and a thermally responsive member mounted on the outside oi' said casing and.connected to said trip element Afor compensating for predetermined changes in temperature.

-6. In a circuit interrupter, relatively movable contact members'ior opening and closing the circuit, operating means including a manually operable means i'or opening and closing said contact members, a bodily movable bimetallic controlelement heated by the current in the circuit. and operable when heated in responseto predetermined current conditions to flex a predetermined amount and cause actuation ofsald contact members, a thermally responsive member connected to said control. element to bodily move saidcontrol element in Vcompensating tor changes in temperature, u stantiallypreventing heat generated at said control element and in said interrupter from aiiect ing said thermally responsive member.

7. In aircuit interrupter, relatively movable contacts for opening and closing the circuit, act'- uating means for opening and closing said con'- tacts, means including. a bodily movable bimetallic trip element heated in response to thecurrent and means for sub-` lease Aof said member and opening of said contacts, a casing for enclosing said elements, 4and a bimetallic member rigidly mounted at one end on the exterior of said casing .and having its free end connected to said trip element for compensating for changes in the surrounding tempera;`

ture.

9. In a circuit interrupter, a casing, relatively movable contacts mounted in said casing, a bl- Vmetallic trip element pivotally mounted in said casing, heated in response to the current ilow in the circuit, said trip element being adapted to ilex in responseto predetermined overload conditions to cause opening oi' said contacts, a blmetallic member rigidly secured at one end on the exterior of said casing, and means including an adjusting screw connecting the free end o! said bimetallic'member to said trip element. said bimetallic member being loperable to compensate for changes in ambient temperature, said adjusting screw being accessible from outside said casing.

-10.'A circuit controlling means comprising a base. a bimetallic control element bodily movable on said base and heated in response to the current flow in the controlled circuit, said element being adapted to be ilexed in response to predetermined overload Aconditions and also ilexed in response' to changes 'in ambient temperature, a thermally responsive member rigidly secured at one end to said base on the opposite side thereof from said control element and having its free end connected to said control element to compensate for ambient temperature movement of said control element.

v 11.In a circuit interrupter, relatively movable contacts, actuating means for opening and closing said contacts, said actuating means including a member releasable to cause automatic opening of said contacts, means for latching said member comprising a pivotally mounted bimetallic trip element heated in response to the current of the circuit,lsaid trip'element being adapted to -ilex when heated a predetermined amount in response to overload currents to cause said latching means to release said releasable member, a second bimetal element rigidly mounted at one end on a ilxed support and having its free'end connected to said pivotally'mounted bimetallic trip element by means including an adjusting screw, said second bimetal element serving to compensate said pivoted bimetallic trip element for changes in ambient temperature, and said adjusting screw being adjustable to vary the lflow inthe circuit, said trip element being adapted to flex apredetermined amount in response to 'predetermined overload conditions to cause opening of said contacts, a bimetallic member rigidly mounted at onefend onfa fixed support, and an adjustable heat insulating connection between the free end of said bimetallic member and said trip element, said bimetallic member being operable to compensate for changes in the temperature surrounding said member.

8.` In a circuit interrupter, vrelatively movable contacts, actuating means for opening and clos'- ing said contacts, a spring biased member releasable to cause opening of said contacts, a pivotally mounted bimetallic trip element heated in response to the-current iiow in the circuit, said trip element being adapted to iiex in response to predetermined overloadconditions to eiiect reamount of latch overlap to thereby adjust the trip characteristic of the breaker.v

12. In a clrcuitinterrupter, a casing, relatively movable contacts in said casing, actuating means for opening and closingsaidl contacts, a pivotally mounted bimetallic trip element" in said casing heated in response to the current of the circuit,

f said trip element being adapted to ilex when heated a predetermined amount in response to overload currents to open said contacts, a second bimetallic element rigidly mounted at one'end on a fixed support and having its free end connected to said pivoted Y bimetallic element to'fcompensate i'or changes in ambient temperature, said second-bimetallic element being substantially-isolated from heat radiation and convection currents from said bimetallic trip element and exposed to the'temperature of the medium outside of the casing.

OLIVER S. JENNINGS.

HABLAN S. GANO.

to cause said actuating means 

